Electrical plug and socket couplings



F eb. l5, 1966 J. EDWARDS 3,235,831

ELECTRICAL PLUG AND SOCKET COUPLINGS Filed Dec. 26, 1962 Y FIG. 7

/NVE/vTo/P 5 JOHN EDWARDS United States Patent O 3,235,831 ELECTRICAL PLUG AND SOCKET COUPLINGS John Edwards, Wellesley Works, Wellesley Road, Wood Green, London, England Filed Dec. 26, 1962, Ser. No. 247,051 Claims. (Cl. 339-61) This invention relates to an electrical plug and socket coupling more particularly of the kind for use in the connection of an electricity supply to an aircraft for servicing purposes as, for example, de-icing, the supply also being used for engine starting.

It is the usual practice to provide a plug fitting on the aircraft, the fitting having two current pins which Iare connected in the circuits of the electrical apparatus involved in the servicing of the aircraft. The fitting also has a third pin which is insulated from the current pins and which has no electrical connection, the pin being shorter in length to that of the current pins. Surrounding the pins collectively is a attened oval sheet metal wall which serves as a shroud and also as -a socket for the insertion of the body of a socket member. The member comprises a rubber molding in which are metal socket tubes to receive the current pins of the plug litting, which tubes are connected to an electricity supply. Molded in the body of the socket member are two socket tubes to receive the current pins of the plug fitting which tubes are connected to an electricity supply. Molded in the body of the socket member are two longitudinallyspaced contacts each arcuate in cross-section, the contacts being insulated one from the other. These contacts are electrically connected by the insulated pin mounted on the plug fitting when the socket member is connected to the fitting. The connection of the arcuate contacts closes an auxiliary circuit whereby the two current sockets are connected to the electricity source for servicing.

Since the insulated pin protrudes to a lesser extent than the current pins, the auxiliary circuit is closed after the initial engagement of the current pins with their respective sockets, also the breaking of the auxiliary circuit is effected while the sockets are still in engagement with their respective pins. Thus, arcing is prevented at the moment of insertion or withdrawal of the socket body, also, the danger from electric shock, by accidental contact with the current sockets, is prevented.

It has been found that the molding of the arcuate contacts in the rubber body has serious disadvantages. The sulphur in the rubber causes corrosion of the usual silver plating of the contacts and the rubber may obstruct the proper contact of the pin with the contacts. Further, the construction has but little strength. If such defects occur, the main circuit may be energized with the result that the equipment may be damaged and injury caused to the operator of the plug. When a socket develops these defects the only remedy is to discard the rubber body and replace it by another. Thus, over a period of time considerable expense is involved.

The object of this invention is to overcome these disadvantages by providing a rubber socket body wherein the arcuate contacts Iare superseded by a removable and insertable contact unit which will not be adversely affected by the sulphur in the rubber and which Will ensure good electrical contact between the pin and the arcuate contacts.

According to this invention a socket for use with an electrical plug and socket coupling comprises a socket body formed from an insulating material, a socket unit insertable in and removable from a hole in the said body, the unit comprising two contact members electrically insulated from each other and arranged to be electrically connected by a plug pin inserted between them, means comprising a separable core of insulating 3,235,831 Patented Feb. 15, 1966 material for retaining the said members in spaced relationship, and a sleeve of insulating material enclosing the said members and having a tight fit in the said hole.

In order that the invention may be clearly understood it will now be described more fully, by way of example, with reference to the accompanying drawings in which:

FIGURE l is a side elevation of a socket body, partly broken away, and showing a socket unit according to the invention;

FIGURE 2 is a plan of the socket body;

FIGURE 3 is a side elevation of the socket unit, the sleeve surrounding the unit being shown in section;

FIGURE 4 is a side elevation of the socket in the direction of the arrow, the sleeve being shown in section;

FIGURE 5 is a section on line V-V of FIGURE 3;

FIGURE 6 is a section on line VI-VI of FIGURE 3 and;

FIGURE 7 is an exploded perspective view of the unit;

FIGURE 8 is an enlarged cross section of the upper end of the socket unit.

Referring to the drawings, a rubber socket body 1 which may be similar to that used in known plug and socket couplings for connection of an electricity supply to an aircraft, has the normal current sockets, indicated at 1A and 1B7 but in place of the molded arcuate contacts the body has a plain bore 1C. Having a tight fit in the bore 1C is a socket unit 2 comprising a pair of elongated contacts 2A each contact of the pair of contacts having a portion 2B which is arcuate in cross section as shown in FIGURE 5. Preferably, formed with the arcuate portion is a tongue 2C which has a flat surface 2D and an opposite convex surface 2E, the radius of which is the same as that of the exterior surface of the arcuate portion. Each tongue 2C lits into a longitudinal groove 3 in a core 3A of insulating material, the tongues when in place, forming a cylindrical surface with the slotted part of the core. Each tongue has shoulders 3E which abut against a shoulder 3C formed by a reduced diameter portion 3D of the core. The radius of the portion 3D yand that of the inside surface of the arcuate portion 2B of each contact correspond, thus the portions 2B fit snugly against the portion 3D of the core. As will be seen, more particularly from FIGURE 3, a space 3F is provided between the end of the reduced diameter portion of the core and the ends of the arcuate portions of the contacts which space constitutes a socket for a conductive pin 3G indicated by dot and dash lines which normally closes the auxiliary circuit through the arcuate contacts.

In order to prevent relative longitudinal displacement of the contacts and core, the latter may have projections 4 which engage in holes 4A in the contacts.

The contacts and core, when assembled, fit tightly in a sleeve 5 of insulating material, the contacts abutting against an internal lip 5A formed in the sleeve. It is preferred that the thickness of the wall of the sleeve should be such that when lateral pressure is applied to the sleeve, the contacts and core assembly are tightly gripped in the sleeve. The ends of the tongues 2C project beyond the sleeve, and form soldering tags 5B for the conductors of the cable of the auxiliary circuit. Alternatively, the tags may have terminal means (not shown) for the connection of the conductors of cables. Isolating the tags is a partition 5C formed at the end of the core. The sleeve is reduced in diameter as at SD and embracing the reduced diameter portion are two split tubular spring circlets 5E. The sleeve is split diametrically as at 5F in the regi-on of the spring circlets thus the circlets exert pressure on the arcuate contacts through the medium of the sleeve thereby assuring good electrical contact between the contacts and the associated pin. It will be apparent that, since the contacts 2A are insulated from each other by the core 3A, an auxiliary circuit may be closed through the contacts 2A when the socket body 1 is applied to an aircraft plug, and the pin 3G of the said plug is inserted between the contacts 2A.

The contact unit, constituted by the contacts, core and sleeve is a ti-g-ht t in the plain bore 1C in Ithe body 1 and due to the resilience of the body, is rmly secured therein, but not to an extent which makes withdrawal and replacement diflicult.

The contacts need n-ot necessarily be arcuate in cross section and may be of any other desired cross section the associated pin having a corresponding cross section. It is to be understood that the core for the contacts will be modified to suit the shape of the contacts.

In order that the socket unit 2 may be secured in the rubber body 1, the unit may have a diametrical pin 6 which passes through a hole 6A in the core 3A and aligned holes 6B in the sleeve 5. The ends lof the pin project beyond the unit and t into holes 6C, on the body. The pin may be formed from a suitable insulating material, or it may comprise a metal screw which engages a thread in the hole 6A in the core. It will be observed from FIGURE 3 that the pin or screw passes through the core clear of the tongues 2C. f

What I claim is:

1. A socket for use with an electrical plug and socket coupling of the kind referred to comprising a socket body formed from a resilient insulating material, a socket unit insertable in and removable from a hole in the said body, the unit comprising two elongated contact members electrically insulated from each other, each member having a portion of arcuate form i-n cross section and a tongue extending from the said portion, the tongue being of less width than that of the said portion, a separable stepped cylindrical core of insulating material, the smaller diameter part of the core providing a mounting for a part of the arcuate portion of each of the said members and the larger-diameter part having opposite longitudinal grooves into which the said tongues t, projections on the vsaid smaller-diameter part engageable in holes in the arcuate portion of each of said members, and a sleeve of insulating material surrounding the said contact members and having a tight t in the hole in said body.

2. A socket for use with an electrical plug and socket coupling of the kind referred to comprising a socket body formed from a-n insulating material, a socket unit insert- 'able in and removable from a hole in the said body, the

unit comprising two contact members electrically insulated from "each other, each member being of arcuate form in cross section, means comprising a separable core of insulating material for retaining the said members in spaced relationship, a sleeve of insulating material surrounding 4the said contact members and tting tightly in the hole in said body, said sleeve having a relatively thin wall portion which is split diametrically, and at least one spring circlet encircling the split portion of said sleeve whereby pressure is exerted on the said members through the medium of the said thin wall portion.

3. A socket for use with an electrical plug and socket coupling of the kind referred to comprising a socket body formed from an insulating material, a socket unit insertable in and removable from a hole in the said body, the unit comprising two elongated contact members each having an arcuate portion, a separable core of insulating material on which Ithe said members are mounted in spaced relationship, inter-engaging means on the said members and core whereby relative longitudinal and rotational displacement is prevented, a sleeve of insulating material surrounding said contact members and tting tightly in the hole in said body, said sleeve having a rela-tively thin wall portion which is split diametrically, and atleast one spring circlet encircling the split portion of said sleeve whereby pressure is exerted on the said members `through the medium of the said thin wall portion.

4. A socket for use with an electrical plug and socket coupling of the kind referred to comprising a socket body formed from a resilient insulating material, a socket unit insertable into and removable from a -hole in the said body, the unit comprising two elongated contact members electrically insulated from each other, each member having a portion of arcuate form in cross section and a tongue extending from the said portion, the ltongue being of less width than that of the said portion, a separable stepped cylindrical core of insulating material, the smaller diameter part of the core providing a mounting for a part of the arcuate portion of each of said members and the larger diameter part having opposite longitudinal grooves into which the said tongues t, projections on the said smaller diameter part engageable in holes in the arcuate portion of each of said members, a sleeve of insulating material surrounding the said contact members and tting tightly in the hole in said body, said sleeve having a relatively thin wall portion which is split diametrically, and at least one split circlet encircling the split portion of said sleeve whereby pressure is exerted on the said members through the medium of the said thin wall portion.

5. A socket for use with an electrical plug and socket coupling of the kind referred to comprising a socket body formed from a resilient insulating material, a socket unit insertable into and removable from a hole in the said body, the unit comprising tw-o elongated contact members, each member having a portion of arcuate form in cross section and a tongue extending from said portion, the tongue being of less width than that of said portion, a separable stepped cylindrical core of insulating material, the smaller diameter part of the core providing a mounting for a par-t of the arcuate portion of each of said members and the larger diameter part having opposite longitudinal grooves into which the said tongues t, projections on the said smaller diameter part engageable in holes in the arcuate portion of each of said members, a sleeve of insulating material surrounding the said arcuate lportions and also the said larger diameter part of said core, the sleeve hav-ing a tight t in the hole in said body, a relatively thi-n wall portion on the sleeve which portion is split diametrically, lat least one split circlet encircling` the split portion of said sleeve whereby pressure is exerted on the said arcuate portions through the medium of the thin wall portion, an extension on each of the said tongues projecting beyond the said sleeve for the connection of conductors to the said contact members, a partition at vone end of said core for isolating the said extensions of the contact members, and a removable securing member for the said unit, insertable in a hole in the said body and Athrough an laligned hole in the core.

References Cited by the Examiner UNITED STATES PATENTS 1,981,460 11/1934 Miller l339-60 2,030,522 2/1936 Johansson 339-19 X 2,163,779 6/1939 Draving 339-220 X 2,214,587 9/1940 Kraut- 339-255 X 2,225,460 12/1940 Porth 136-135 2,502,634 4/1950 Smith 339-212 3,076,163 1/1963 Nodge et al. 339-4 3,085,220 4/1963 Sitz 339-19 X ALBERT H. KAMPE, Primary Emniner.

JOSEPH D. SEERS, Examiner. 

2. A SOCKET FOR USE WITH AN ELECTRICAL PLUG AND SOCKET COUPLING OF THE KIND REFERRED TO COMPRISING A SOCKET BODY FORMED FROM AN INSULATING MATERIAL, A SOCKET UNIT INSERTABLE IN AND REMOVABLE FROM A HOLE IN THE BODY, THE UNIT COMPRISING TWO CONTACT MEMBERS ELECTRICALLY INSULATED FROM EACH OTHER, EACH MEMBER BEING OF ARCUATE FORM IN CROSS SECTION, MEANS COMPRISING A SEPERABLE CORE OF INSULATING METERIAL FOR RETAINING THE SAID MEMBERS IN SPACED RELATIONSHIP, A SLEEVE OF INSULATING MATERIAL SURROUNDING THE SAID CONTACT MEMBERS AND FITTING TIGHTLY IN THE HOLE IN SAID BODY, SAID SLEEVE HAVING A RELATIVELY THIN WALL PORTION WHICH IS SPLIT DIAMETRICALLY, AND AT LEAST ONE SPRING CIRCLET ENCIRCLING THE SPLIT PORTION OF SAID SLEEVE WHEREBY PRESSURE IS EXERTED ON THE SAID MEMBERS THROUGH THE MEDIUM OF THE SAID THIN WALL PORTION. 